A bonding wire is used to connect an electrode pad on a semiconductor chip and an external electrode such as a lead frame. One end of the bonding wire is connected to the electrode pad, and the other end is connected to the external electrode. In order to improve the reliability of the bonding wire, for example, a gold-containing metal layer with high oxidation resistance and stability is applied to a surface of the electrode pad. On the other hand, the adhesion force between the gold-containing metal layer and the base metal layer becomes weak, which may result in a lower bonding yield rate.